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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. IceCube alert 141029_8144692 retraction
  2. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  3. GRB 250614A: Fermi GBM Final Real-time Localization
  4. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  5. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  6. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  7. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  8. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. Fermi trigger No 771494087: Global MASTER-Net observations report
  10. sb25061218: Swift-XRT observations
  11. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  13. sb25061207: EP-FXT follow-up observation and afterglow candidate
  14. GRB 250612B: Fermi GBM Observation
  15. EP250612a: SVOM/VT optical candidate
  16. Fermi trigger No 771424081: Global MASTER-Net observations report
  17. EP250612a: Global MASTER-Net observations report
  18. GRB 250612C: Fermi GBM Observation
  19. sb25061218: SVOM detection of a X-ray transient
  20. sb25061207: Swift-XRT observations
  21. EP250612a/GRB 250612B: JinShan optical upper limit
  22. EP 250612a: AST3-3 Yaoan Optical Observation
  23. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  24. sb25061207: SVOM/VT optical counterpart
  25. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  26. GRB 250610B: Swift-XRT refined Analysis
  27. GRB 250612C: Fermi GBM Final Real-time Localization
  28. EP250610a: Upper limit from Fermi-GBM Observations
  29. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  30. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  31. EP250612a: Einstein Probe detection of an X-ray transient
  32. GRB 250610B: Liverpool Telescope continued monitoring
  33. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  34. sb25061207: SVOM detection of a X-ray transient
  35. EP250610a: continuous follow-up observations with EP-FXT
  36. GRB 250610B - SVOM/ECLAIRs refined analysis
  37. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  38. Swift GRB250612.04: Global MASTER-Net observations report
  39. Fermi GBM Sub-Threshold Detection of GRB 250610B
  40. GRB 250610B: Swift/UVOT Detection
  41. EP250610A: Swift/UVOT Upper limits
  42. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  43. EP250610a: TNG NIR upper limit
  44. GRB 250610B: REM optical/NIR observations
  45. EP250610a: Liverpool Telescope optical upper limits
  46. GRB 250610B: SVOM/VT optical shallow decay
  47. GRB 250610B: additional Liverpool Telescope optical observations
  48. GRB 250610B: SVOM/GRM analysis
  49. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  50. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  51. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  52. GRB 250610B: Swift-XRT counterpart detection
  53. GRB 250610B: SVOM/VT optical counterpart
  54. GRB 250610B: LT detection of the optical counterpart
  55. GRB 250610B: OHP/T120 optical counterpart candidate
  56. GRB 250610C: Fermi GBM Final Real-time Localization
  57. GRB 250610B: GOTO optical upper limit
  58. EP250610a: Global MASTER-Net observations report
  59. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  60. GRB 250610B: SVOM detection of a long burst
  61. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  62. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 250610A: Fermi GBM Final Real-time Localization
  64. GRB 250605A: Swift-BAT refined analysis
  65. EP250610a: SVOM/VT optical upper limit
  66. EP250610a: REM optical/NIR observations
  67. GRB 250609A: Fermi GBM Observation
  68. GRBAlpha reentry on June 9, 2025
  69. EP250610a: Swift-XRT counterpart detection
  70. EP250610a: COLIBRÍ optical upper limit
  71. EP250610a: Einstein Probe detection of an X-ray transient
  72. Fermi trigger No 771072240: Global MASTER-Net observations report
  73. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  74. GRB 250605A: Swift/UVOT Upper Limits
  75. The EP-WXT trigger 01709178283 is likely a flaring star
  76. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  77. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  78. GRB 250527C: CrAO Optical Upper Limit
  79. GRB 250609A: Fermi GBM Final Real-time Localization
  80. GRB 250607A: SVOM/GRM observation of a long burst
  81. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  82. The EP-WXT trigger 01709178244 is likely a flaring star
  83. GRB 250607A: Fermi GBM Final Localization
  84. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  85. The EP-WXT trigger 01709178069 is likely a flaring star
  86. GRB 250605A: SVOM/VT optical upper limit
  87. GRB 250605A: Swift-XRT refined Analysis
  88. EP/WXT 01709177873: GOTO observations confirm stellar variability
  89. GRB 250605A: Enhanced Swift-XRT position
  90. Fermi GRB 250606A: Global MASTER-Net observations report
  91. GRB 250606A: Fermi GBM Final Real-time Localization
  92. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  93. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  94. GRB 250602A: GECAM detection
  95. Fermi trigger No 770867684: Global MASTER-Net observations report
  96. The EP-WXT trigger 01709177873 is likely a flaring star
  97. GRB 250605A: LT optical observations
  98. GRB 250605A: Swift detection of a burst
  99. Swift GRB250605.79: Global MASTER-Net observations report
  100. Konus-Wind detection of GRB 250601A

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